Physics @ Berkeley
Events in Physics
Title: Neutron-detected tomography of impurity-seeded superfluid helium    (Colloquia)
Start Date: 02/14/2005
Time: 4:30 pm
Location: 1 LeConte Hall
Speaker: Prof Mike Hayden
Affiliation: Dept of Physics, Simon Fraser University
Contact Person: K. Lee   (510) 642-3034
Details: The spectacular macroscopic quantum behaviour exhibited by liquid helium at temperatures below 2.17 K has fascinated physicists since evidence for hydrodynamic flow without dissipation, the hallmark signature of a superfluid, was first announced in 1938. To this day superfluidity in liquid helium, and more generally in quantum fluids, constitutes an important discipline of research with broad implications, from understanding neutron stars to developing atomic lasers. Despite the maturity of the field, it has proven remarkably difficult to ‘map’ or ‘image’ superfluid flow in liquid helium with significant spatial resolution. In part, this is because the liquid is naturally self-cleaning. At low temperatures, almost any neutral atom or molecule (other than 3He) that is injected as a contrast agent will aggregate in the bulk or adsorb to the walls of the container. In this talk I will describe a neutron radiography technique that has enabled the first-ever multidimensional tomographic visualization of 3He impurity distributions in superfluid liquid 4He. At temperatures of order 1 K these impurities couple to the normal (non-superfluid) component of the liquid, allowing us to probe underlying velocity fields with millimetre-scale resolution.

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